1986 f150 thumpy noise

My truck just started making a strange noise, that I can feel, in the last couple of days. It doesn't do it when I just have the engine running. it only happens when I go down the road. It seems propertional to the speed of the vehecle not the speed of the engine. Sometimes I don't feel it when I am going at speeds in excess of 45 mph. I can really feel it when I accelerate slowly. It is a very consitent rythmen sound that I can feel.

I orignial thought it might be the transmission however, the noise keeps happenening at all gear ranges. So then I thought maybe differenteil or a tire perhaps. Has Anyboody got any ideas?

Someone suggested that it could just be cold. However once the truck warms up it still does it.

 

Did you check your tire balance? Sometimes the weights will come off and throw the balance out of whack.

Is there a noticeable part of the truck that this is coming from? Also, where do you notice this feel? The wheel, brakes, butt sensor?

 

sounds like ply seperation

 

I did check the tires this morning. I noticed the right front was loose on its bearings so it took it apart and repacked them. Then I got them good and snug. I checked each tire also by jacking up that wheel and slowley rotating it. Somebody also suggested that it could be a nail or a bolt in one of the tire. However I did not find any problems. All the tires appear to be good. The front ones are older than the rears. They were sitting at 32.5 psi and the rears were at 33 psi. So i went ahead and brought them up to 34psi. They are rated 35. I took into account the temperature at the time was 46 so I allowed a one psi increase once the temperatue comes up.

I could only feel the bump from my left foot. I think it might have just been the bearings. If not I will get the tires balenced.